Performing Department
(N/A)
Non Technical Summary
?Chemical signals play a crucial role in mediating interactions between plants and insects, and researchers have found that manipulating these cues for alternative pest management is a promising and impactful area of study. Extensive research has focused on utilizing plant volatiles and pheromones induced by herbivores to influence pest behavior and mitigate damage to crops. Recent findings have demonstrated that chemical cues emitted by predatory insects can also induce alterations in herbivore physiology and behavior, leading to reduced overall pest damage. Nevertheless, using predatory insect cues as a pest management tool remains largely unexplored.In this project, we will determine which odors from predatory lady beetles allow aphid pests to determine the threat of predation. We will expose all of the individual compounds that are produced by ladybugs to the aphids antennae which will reveal the crucial compounds for behavioral and physiological changes in aphids. We can then expose aphids to the odor blend and assess their feeding, reproduction, assimilation of nutrients, population growth and other traits. Lastly, we will explore how this odor blend affects aphids and other organisms in the field.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
Chemical signals are pivotal in shaping the interactions between plants and insects, offering a promising avenue of research for innovative pest management strategies. Researchers have long focused on harnessing plant volatiles and insect pheromones to influence pest behavior and minimize crop damage. Recent studies have uncovered the potential of predatory insect cues in altering herbivore physiology and behavior, yet exploiting these cues for pest management remains largely unexplored.Our initial findings reveal that chemical cues from lady beetles significantly impact aphid host-plant selection, hinder aphid feeding, decrease aphid reproduction, and prompt aphid dispersal. However, to fully leverage this discovery, we must identify the specific compounds responsible for eliciting these behavioral changes, evaluate the efficacy of synthetic predator blends on key pest traits, and understand how scaling up the use of these blends impacts aphid population dynamics, biological control, plant vigor, and the broader arthropod community in agricultural fields.These findings pave the way for a novel pest management approach utilizing synthetic blends of predatory insect semiochemicals, promising reduced pest damage and increased yield for growers. Although manipulating predator chemical ecology holds great potential for integrated pest management (IPM), there remains a critical need to pinpoint bioactive compounds, assess their impact on aphid behavior, and understand their implications for plant health and ecological interactions in field settings.Aligned with our overarching hypothesis, our proposed research aims to:Objective 1: Investigate the bioactivity of components within the H. axyridis semiochemical blend on aphids.Objective 2: Assess the influence of isolated predator semiochemical blends on aphid performance, feeding behavior, and assimilation efficiency.Objective 3: Evaluate the effects of the isolated predator semiochemical blend on aphid population dynamics in field conditions.Objective 4: Examine the broader arthropod community responses and crop yield in response to the isolated predator semiochemical blend in open-field settings.By unraveling the mechanisms through which predator cues mitigate pest performance and safeguard crops, this project will offer a novel, sustainable approach to pest management, transferrable to various agricultural systems. Ultimately, this endeavor advances the realm of plant health and production by enhancing the efficacy of biological control strategies.
Project Methods
Objective 1:Examine components of theH. axyridissemiochemical blend for bioactivity in aphidsAphid EAGs will be run in the Chemical Ecology Core Facility at Penn State where we have developed and tested methods forM. persicaehave been established. In short, we will assess aphid female antennal responses toH. axyridisSolid Phase Micro-extraction (SPME) volatile headspace collections. One hundred nanograms of an aphid alarm pheromone standard, (E)-Beta farnesene), will be injected on the GC as a separate positive EAG control. Since aphids disperse in both apterate (wingless) and alate (winged) morphs by crawling between plants or flying, respectively, we will test a total of 15 individuals from both adult morphs. The relative EAG amplitudes from female aphid antennae in response to the different natural enemy volatile compounds will be assessed using custom software designed by Dr. Andrew Myrick of the Center for Chemical Ecology.Objective 2:Determine the role of the isolated predator semiochemical blend on aphid performance, feeding behavior, andassimilation efficiencyFeeding Behavior - To test effects of exposure to theH. axyridissemiochemical blend on aphid feeding, we will use an Electric Penetration Graph (EPG). The EPG is a closed-circuit electrical detection system used to characterize real-time feeding in phloem-feeding insects, such as aphids. Adult apterate and alate aphids will be randomly chosen from colonies and starved for 1 hour before wiring is set up. Aphids will be connected to a probe using ultra-finegold wire and silver glue. Copper electrodes will be placed in the soil at the base of the collard host plants to complete the circuit through the EPG system. The plants will be enclosed in a metal mesh Faraday cage. Using EAG data, we will create a semiochemical odor blend with bioactive compounds in realistic ratios obtained from our previous VOC collections and resulting GC/MS data. The final blend will be diluted with methanol from pure compounds to achieve the appropriate concentrations and methanol will serve as the control odor source. The blend will be placed in a 5/8 dram, brown glass vial with diffuser top and placed in the base of the potted plant's soil. Aphid probing and feeding behaviors will be recorded for 8 hours using the Stylet+ software, and recordings will only be included in the final analysis if a minimum of 3 hours of activity was captured. We will repeat this assay until we have 20 successful replicates per treatment with each aphid morphotype. The resulting waveforms from the recordings will be characterized using Stylet+ A, and the labels will be converted into either time spent in each feeding phase or number of incidences of an action using an automatic parameter calculating macro.Assimilation Efficiency-Honeydew production by individual adult aphids of each morphotype will be evaluated in a clip-cage arena used to restrict aphid movement while providing aphids with leaf material that was still connected to the plant. Arenas will be created by cutting a hole in the side of an 11.43 × 8.89 × 5.08 cm sealed container, and a single collard leaf will be inserted into the hole and secured in place with a cotton ball. One adult alate or apterous aphid will be randomly chosen from the colony was placed on the underside of the leaf. Aluminum foil will be placed at the bottom of the arena to catch the honeydew falling from the aphid. The center of the container lid was cut out and replaced with very fine fabric mesh (680µm aperture)to allow ventilation. As in objective 2a, the blend will be placed in a 5/8-dram, brown glass vial with a diffuser top and placed in the base of the potted plant's soil. Each of the treatments will be replicated 30 times. After 24 hours we will count the number of honeydew drops on the foil. We will collect honeydew again at 48h and identify the sugars and amino acid content/composition using high-performance liquid chromatography (HPLC). We will also repeat this sugar/amino acid evaluation on the plant tissue. After one week of aphid feeding, 20 adult aphids will be collected from each plant and brought to the lab to be weighed.Objective 3:Test how the isolated predator semiochemical blend affects aphid population growth in a field settingIn order to assess the impact of consumptive and non-consumptive effects on aphid population abundance we will use field cage mesocosms. At the farm, we will till a 1-acre plot and establish a randomized array of 0.5m3field cages. Each cage will have one 4-week-old collard plant placed in the center. A group of20 adult aphids will be added to the collard plant within the field cage. After allowing the aphids to settle for 24 hours, each cage will receive either 1) a diffuser vial of methanol (predator-free control) 2) two free-moving (lethal)H. axyridis+ a brown diffuser vial with the semiochemical blend, or 3) a brown diffuser vial with the semiochemical blend.The treatments will be replicated 15 times for a total of 45 cages.Aphid abundance will be assessed on days 3 and 7, and then weekly for 6 weeks to cover the typical collard growing period.Harmonia axyridiswill be checkedevery 3 daysfor mortality and replaced as needed. Theresponse of aphid abundance to thenatural enemycue treatments will be assessed over timeand compared across treatments.Objective 4:Assess how the isolated predator semiochemical blend affects arthropod community responses and crop yield in the open fieldTo assess the influence of isolated predator semiochemicals on pest colonization, pest population growth, predation rate, and crop yield, we will set up a large field experiment with two treatments: control (unmanipulated), chemical cue (semiochemical odor blend fromH. axyridis, as described above). The land will be subdivided into 30 experimental plots, measuring 8 x 8m, each separated from other plots as well as the field edge by 10m. All experimental plots will be planted following commercial standards with 1 m spacing between collard transplants within a row and 1m spacing between rows. Each plot will consist of approximately 100 plants which will serve to attract and sustain naturally occurring insect populations over the experimental period.Among the planted collards in each experimental plot, the central, collard will be assigned one of the two treatments mentioned above: 1) control (methanol control dispenser fixed to a bamboo stake that will be placed adjacent to the plant), 2) semiochemical blend (odor blend fromH. axyridis, in a custom dispenser fixed to a bamboo stake that will be placed adjacent to the plant). Sampling will occur on the central plant as well as plants in each cardinal direction from the center at 1, 2, 4 and 8m away from the central hole, for a total of 17 sampled plants per plot.This will result in 17 plants sampled per replicate plot, sampled over the 6-week growing period. Sampling in each cardinal direction will allow us to not only assess the efficacy of our treatment, but also account for any spatial patterns as we move away from the dispenser.For each trial we will assess aphid colonization, other herbivorous pest colonization, natural enemy recruitment, diversity, and abundance, predation rate (egg cards, sentinel prey), and end-of-season yield.